Back to square one

In a matter of months or years,the effort has come undone,and the patient is fat again. It has always seemed strange to me, says Proietto,a physician at the University of Melbourne. These are people who are very motivated to lose weight,who achieve weight loss most of the time without too much trouble and yet,inevitably,gradually,they regain the weight.

Anyone who has ever dieted knows that lost pounds often return,and most of us assume the reason is a lack of discipline or a failure of willpower. But Proietto suspected that there was more to it,and he decided to take a closer look at the biological state of the body after weight loss.

Beginning in 2009,he and his team recruited 50 obese men and women. The men weighed an average of 233 pounds; the women weighed about 200 pounds. Although some dropped out of the study,most of the patients stuck with the extreme low-calorie diet,which consisted of special shakes called Optifast and two cups of low-starch vegetables,totaling 500 to 550 calories a day for eight weeks. Ten weeks in,the dieters lost an average of 30 pounds.

At that point,the 34 patients who remained stopped dieting and began working to maintain the new lower weight. Nutritionists counseled them in person and by phone,promoting regular exercise and urging them to eat more vegetables and less fat. But despite the effort,they slowly began to put on weight. After a year,the patients already had regained an average of 11 of the pounds they struggled so hard to lose. They also reported feeling far more hungry and preoccupied with food than before they lost the weight.

While researchers have known for decades that the body undergoes various metabolic and hormonal changes while its losing weight,the Australian team detected something new. A full year after significant weight loss,these men and women remained in what could be described as a biologically altered state. Their still-plump bodies were acting as if they were starving and were working overtime to regain the pounds they lost.

For instance,a gastric hormone called ghrelin,often dubbed the hunger hormone,was about 20 per cent higher than at the start of the study. Another hormone associated with suppressing hunger,peptide YY,was also abnormally low. Levels of leptin,a hormone that suppresses hunger and increases metabolism,also remained lower than expected. A cocktail of other hormones associated with hunger and metabolism all remained changed compared to pre-dieting levels. It was as if weight loss had put their bodies into a unique metabolic state,a sort of post-dieting syndrome that set them apart from people who hadnt tried to lose weight.

What we see here is a coordinated defence mechanism with multiple components all directed toward making us put on weight, Proietto says. This,I think,explains the high failure rate in obesity treatment.

While the findings from Proietto and colleagues,published this fall in The New England Journal of Medicine,are not conclusive the study was small and the findings need to be replicated the research has nonetheless caused a stir in the weight-loss community. For years,the advice to the overweight and obese has been that we simply need to eat less and exercise more. While there is truth to this guidance,it fails to take into account that the human body continues to fight against weight loss long after dieting has stopped. This translates into a sobering reality: once we become fat,most of us,despite our best efforts,will probably stay fat.

The National Weight Control Registry tracks 10,000 people who have lost weight and have kept it off. We set it up in response to comments that nobody ever succeeds at weight loss, says Rena Wing,a professor of psychiatry and human behavior at Brown Universitys Alpert Medical School,who helped create the registry. We had two goals: to prove there were people who did,and to try to learn from them about what they do to achieve this long-term weight loss. Anyone who has lost 30 pounds and kept it off for at least a year is eligible to join the study.

Wing says she agrees that physiological changes probably do occur that make permanent weight loss difficult,but the larger problem is environmental,and that people struggle to keep weight off because they are surrounded by food. We live in an environment with food cues all the time, Wing says. Weve taught ourselves over the years that one of the ways to reward yourself is with food. Its hard to change the environment and the behavior.

Kelly Brownell,director of the Rudd Center for Food Policy and Obesity at Yale University,says that while the 10,000 people tracked in the registry are a useful resource,they also represent a tiny percentage of the millions who have tried unsuccessfully to lose weight. All it means is that there are rare individuals who do manage to keep it off, Brownell says. You find these people are incredibly vigilant about their weight. Years later they are paying attention to every calorie,spending an hour a day on exercise. They never dont think about their weight.